url= "http://desk.zol.com.cn/"
#第一种个人觉得好用方便
req = urllib.request.Request(url)
req.add_header("User-Agent","Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36")
#req.add_header()  要注意不是headers
print(req.headers)
#这样就会返回刚设置的headers

#第二种
url= "http://desk.zol.com.cn/"
head = {}
head['User-Agent'] = 'Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36'
#把hedaers 做为一个定典
req = urllib.request.Request(url,headers = head)
print(req.headers)
#这样也会返回headers